Archie Miles's widow was played by Rosanna Huffman, aka Mrs. Richard Levinson (one of at least seven MSW appearances)?
And in this same episode:
Harry's motherly secretary was Margery Nelson, aka Mrs. William Link?
Stuff like this used to happen quite a bit on series like Murder, She Wrote; it was part of the fun back in the day.
Just for fun, while you're here, you might like to check out the bosses's wives credits here; both Rosanna Huffman and Margery Nelson were talented actresses, who worked whenever they wanted to, and commanded respect within the industry (as did their writer-producer husbands, come to that ...)
Happy Hunting!